With Amazon, users can keep a copy as well, I just don't think that users would do this. If you don't go out of our way to keep a copy, the book will be gone from all your devices as soon as they are connected to the internet again. I guess sellers just need to trust their customers if they want to offer returns.

My purchases from Amazon get dowloaded to my computer. Then I run it through Calibre with Alf's Plugins and convert them to epub. They are then added to my Nook Color and backed up on at least two hard drives. Let Amazon try to take them back.
Apache